Implement FileChooser portal proxy with virtiofsd mount

flake.nix

@@ -15,7 +15,13 @@
         pkgs = import nixpkgs {
           inherit system overlays;
         };
-        
+
+        buildEnvVars = {
+          BIN_XDG_PERMISSION_STORE = "${pkgs.xdg-desktop-portal}/libexec/xdg-permission-store";
+          BIN_XDG_DOCUMENT_PORTAL = "${pkgs.xdg-desktop-portal}/libexec/xdg-document-portal";
+          BIN_VIRTIOFSD = "${pkgs.virtiofsd}/bin/virtiofsd";
+        };
+
         rustToolchain = pkgs.pkgsBuildHost.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
         rustPlatform = pkgs.makeRustPlatform {
           cargo = rustToolchain;
@@ -32,11 +38,13 @@
               "busd-0.4.0" = "sha256-UzTclEJ8lRMmiuLJJi+gsm7vkx+MLfnDdi5s9OVT1HE=";
             };
             buildAndTestSubdir = crate;
+            env = buildEnvVars;
           };
       in
       {
         devShells.default = pkgs.mkShell {
           buildInputs = [ rustToolchain ];
+          env = buildEnvVars;
         };
 
         packages.sidebus-agent = rustPackage "sidebus-agent";
@@ -58,6 +66,14 @@
             };
             documentation = [ "https://git.clan.lol/valpackett/sidebus" ];
           };
+          systemd.mounts = [
+            {
+              type = "virtiofs";
+              what = "vm-doc-portal";
+              where = "/run/vm-doc-portal";
+              wantedBy = [ "multi-user.target" ];
+            }
+          ];
         };
       }
     );